It said it was "seriously concerned" about the impact of the action. Health unions are protesting over the public-sector pay cuts.

The HSE has received notice of industrial action from the Irish Nurses and Midwives Organisation, Impact and the Craft Group of Unions.

It met the unions yesterday in a bid to draw up contingency plans.

In a statement, the HSE said the health service was "an essential and critical service" and therefore it had met the unions to seek an exemption from the action but that this request had been turned down.

IMPACT's national secretary, Kevin Callinan, said in a letter to the HSE that the request could not be granted because health was the biggest sector in the public service.